Website Summary

8/3/2019 Website Summary

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R.Sonnenfeld -- NM Tech -- Physics Dept -2006

Ben Franklin in the 21st Century

Richard Sonnenfeld

Physics Department &Langmuir Laboratory for Atmospheric Physics

New Mexico Institute of Mining and Technology

(Photo courtesy of Harald Edens)


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Lightning Effects

Understanding of lightning effects on climate change(N2O production)

Improved lightning rods

Lightning resistant aircraft

Lightning warning systems / tornado warnings?

Global lightning location networks

Lightning Research Products

Lightning kills approximately 100 people/year in US.

Costs $4-5 Billion/yr in disrupted power lines, destroyedelectronics.

Lightning sets off ammunition dumps, fumes, and minegasses.


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Franklins contributions to lightning science

Lightning is an electricalphenomenon, governed bythe same principles aslaboratory staticelectricity.

Most lightning strokescarry negative charge to

ground, though somemove positive charge toground.

A noticeable electric fieldis produced under anactive storm.

(Photo courtesy of Harald Edens)(Photo courtesy of Harald Edens)


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Lightning facts we know now

40 flashes/second on Earth.

Peak current I=100,000 Amps

Voltage V=100 Million Volts

Charge transfer Q=20 Coulombs

Energy E= 1 billion joules

(300 kWatt-hours) Channel radius r=1 cm

Stepped Leader velocity 0.001c

Dart Leader velocity 0.1c

Return Stroke velocity 0.5c

(Photo courtesy of Harald Edens)(From Uman, All AboutLightning -- 1971)


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Benjamin Franklin and the

Sentry Box Experiment


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Corona Discharge(Courtesy of H. Edens)

Streamers(Courtesy of J. Kronjaeger)

Leaders and Streamers

Impact Ionization(From cosmicray.bnl.gov)


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Streak Camera

Photography

L. Salanave, Lightning and ItsSpectrum, (1980).


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Lightning Launched

Upward from Structures

From: L. Salanave, Lightning and Its

Spectrum, Univ. of Arizona Press, (1980).


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Triggered Lightning (Unintentional)

Aircraft at Kamatsu Air Force Base (Courtesy of Prof. Zen Kawasaki).


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Commercial aircraft at Kamatsu Air Force Base (Courtesy of Prof. Zen Kawasaki).


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Lightning Rods

(Air terminals)

Offer small zone of protection

(20 m radius rolling sphereSee NFPA 780).

Are preferentially hit if launch

upward leader.

Provide a highly conductive path

to ground.

Do NOT discharge the clouds.

No Breakthrough lightning

rod has been shown to protect

large areas.

Prof. C. Moores rod research at Langmuir Laboratory


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Lightning Connection

Process

From: P. Krider, Physics of Lightning,

National Academy Press, (1986).


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Blunt vs. Sharp

Rods

From Moore et. al, Lightning Rod

Improvement Studies JAM, 39, (2000)


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Triggered Lightning

Can be usedto study

lightningeffects

Bring thelightning to

your home/airplane /computer /power plant.

A groundedwire trailsbehind a

rocketLangmuir Laboratory lightning triggering experiment


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Is lightning possible?

Where does the energy come from?

Need 1 billion joules in 1 km^3 of air


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Energy Source for Lightning (and weather!)

Need 1 billion joules in 1 km^3 of air Energy Source 1 -- Moisture

Moist air in New Mexico has 1 g of water vapor in 1 m^3

Heat of condensation of steam is 2300 kJ/kg If all the vapor in 1 km^3 condensed, it would produce 2300

billion Joules (2300 GJ), enough for 2300 lightning strokes.

Energy Source 2 -- Buoyancy Hot air balloons use 100 C temperature difference to get lift.

Moist air becomes 2-3 C warmer than dry air as it rises.

It is 1% less dense than dry air. 1 km x 1 km x 1 km that is 3 C warmer than surrounding

has Buoyant Force=1.3E10 N*0.01=1.3E8 Newtons

Energy for 1 km ascent = 130 GJ enough for 130 strokes.


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Atmospheric Instability

From Weather2010 project, Univ. Illinois and Urbana-Champaign


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Convective Available Potential Energy (CAPE)

From Weather2010 project, Univ. Illinois and Urbana-Champaign


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So Lightning needsWater vapor, convection,

and updrafts. Lightning likes SEVERE

Weather!


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Tornado Nowcasting with the Alabama

Lightning Mapping Array

Intra-cloud lightning peaks just before a

tornado touches down.


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Lightning is

associated with

Hurricane Eyewall

intensification

Data from EOSNewsletter of AGU.

Work by Los

Alamos lightning

group.(X. Shao et al.)


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R.Sonnenfeld -- NM Tech -- Physics Dept -2006Analogy between Gravity and Static Electricity


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Electric field detectionE100 Field meter by Prof. W. Winn, New

Mexico Tech


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How do storms electrify?Charge

Density

(nC/m^3)

From Marshall and Rust, Electric Field

soundings through thunderstorms, Journal

of Geophysical Research, (1991)

Water drops & ice crystals carry charge.

Gravitational settling separates unlikecharges.

Updrafts provide the power to cause many

particle collisions that transfer charge


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Evidence for Non-Inductive Charging

The negative charge center in storms is always

found around the 10C Isotherm.

From P.R. Krehbiel,

The Electrical Structure of Thunderstorms

National Academy Press (1986)


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From Moore and Vonnegut, TheThundercloud (R.H. Golde, editor) (1977)

Electrical Activity of a Small Mountain Storm


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R.Sonnenfeld -- NM Tech -- Physics Dept -2006New Mexico Tech

Lightning Mapping Array (LMA)

Uses a network of12 televisionreceivers tuned to66 MHz.

Lightning radiopulses are

correlated in timebetween stations.

Location in skyand emission timeare fit andplotted.

Images intra-

cloud (IC) flashes


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R.Sonnenfeld -- NM Tech -- Physics Dept -2006New Mexico Tech

Lightning Mapping Array (LMA)

Lightning initiatesin high-field regionbetween charge

centers. Lightning spreads

out horizontally as itdrains charge

centers.

R S f ld NM T h Ph i D t 2006


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Bolt from the blue

LMA animation from RonThomas, EE Dept, NewMexico Tech

R S f ld NM T h Ph i D t 2006


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From Sonnenfeld, Battles,Lu and Winn, J. Geophys.

Res., 2006 (submitted)

R Sonnenfeld NM Tech Physics Dept 2006


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R Sonnenfeld -- NM Tech -- Physics Dept -2006


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From Sonnenfeld, Battles,Lu and Winn, J. Geophys.

Res., 2006 (submitted)

R Sonnenfeld -- NM Tech -- Physics Dept -2006


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R.Sonnenfeld NM Tech Physics Dept 2006



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R.Sonnenfeld NM Tech Physics Dept 2006


Li ht i


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Lightning

Observations fromSpace



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Summary

Apparently separate lightning flashes can beattached to the same channel.

The majority of lightning flashes do not connectto ground. They remain in the clouds.

Lightning connects to the ground in short steps.

The stepped leader often fails to connect, thesuccessful ones create the flash and bang that we

experience.

If a cloud is charged, we can trigger lightning

(Aircraft do this on their own)


S


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Summary

The Earth always has a small fair-weatherelectric field, which is kept charged by lightning.

By measuring electric field, we can predict that

lightning is imminent.

Most of Earths lightning occurs over land, not

ocean. Most storms have a main negative positive charge

near freezing level, with a positive charge at

higher altitude.

Lightning initiates between major charge centers.



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References

Appetizer

[Uman71] All About Lightning, Martin A. Uman, Dover Books, (1971)

Main Meal

[Uman01] The Lightning Discharge, Martin A. Uman, Dover Books,

(2001), 2nd edition.

Roman Orgy

[Rakov03] Lightning: Physics and Effects Vladimir Rakov and Martin A.

Uman, Cambridge University Press, (2003).



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Unanswered Questions

What REALLY is the charging mechanism? (Ice/water

tribology) Is ice required for lightning?

What triggers lightning strikes? (Cosmic Rays)

Does lightning trigger precipitation? (Rain gush)

How does the charge move in a lightning channel?

Can a more effective warning or protection system bedevised?

Can lightning be used to predict tornadoes?

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